Best feature : board short loop, don't buy a top w/o one
Fit: I wear size L wetsuits, I'm 6-1 185.  I'd say if you are really buffed up go a size up. To prevent constant flushing these need to be tight.
Use: I use it for mornings and evenings in summer when water is above 68.

Worst feature: getting it on

This is the second one I have purchased within weeks. The first one was beyond expectations. Being in the deep water pool sometimes twice a day, I needed one that was dry for the second use. These are so warm that it's possible to work up a sweat. Looking forward to this summer for the early morning ski trips at the lake where the water can be a bit brisk.
You have to learn how to put this on as it is near impossible to adjust the sleeves after you put it on. Easy to align the graphics on the sleeve with the top side of your arms from your wrist to elbow and then over your head. Fits like a second layer of skin. The rear zipper is a plus but could be longer for ease of exit.
As with the syncro shorts the both go into the washer for a 30 min. rinse and spin after being in the pool. Be sure the hook side of any velcro is covered or closed as it will damage the interior lining of the jacket.
A note on sizing, this will feel really small when first put on. Go buy the sizing chart as it is accurate.
Thanks, Jim